The separation of excavated material into usable types of material such as, for example, sand, gravel and rock, has been performed by utilizing a number of methods and apparatus. For example, the material separating method and apparatus shown in U.S. Pat. No. 5,244,098 discloses a frame having a tall end and a short end, a vibrating separating screen as a separating surface within the frame, and a fixed angle feed directing plate which functions as a funneling surface to direct feed material into the separating surface at the tall end of the frame. Another example is shown in U.S. Pat. No. 4,197,194 which describes a portable loam screening apparatus which includes a generally square shaped shaker screen supported by a box-like frame having a tall end and a short end. When coarse material is dumped onto the shaker screen, the coarse material falls from the lower end of the shaker screen outside the frame while the loam passes through the shaker screen to within the box-like frame.
Other examples of separating methods and devices are shown in U.S. Pat. Nos. 3,307,698, 4,960,510 and 5,100,539. U.S. Pat. No. 3,307,698 discloses a portable oscillating rock separator having an inverted pyramidical hopper and a sloping grid covering the hopper. Although the sloping grid includes a series of parallel longitudinal rails that are positioned and assembled by a journal tube and a cross plate, the screen is not disclosed as being removable.
U.S. Pat. No. 5,100,539 describes a dual screen apparatus and method for sizing and separating particles of a material. The apparatus includes a stand and a frame with suspension assemblies attached to the stand and the frame for movably suspending the frame on the stand. Further, a pair of inclined screens are removably mounted in a pair of screen boxes which are removably mounted on the frame such that each of the screens slopes downwardly from an intermediate portion of the frame toward an end of the frame. A motor is also mounted on the frame for vibrating for vibrating the frame and the attached screens. Although both the screen boxes and inclined screens are removably mounted, neither of these elements includes a feature for aiding in the positioning and removal of the elements within and from their respective locations within the apparatus.
U.S. Pat. No. 4,960,510 discloses a screening apparatus having a screen grid with a plurality of exchangeable screen elements. The screening apparatus includes a screen grid where sieve elements directly contact one another at the top side of their surfaces to provide a continuous surface having sieve openings and separators or retaining bars are present on their undersides for removably boshing the screen elements to the carrier framework. This apparatus functions to make the active sifting surface of the screen grid in a screening apparatus as large as possible by incorporating the marginal resting areas of the screen elements into the acting sifting surface and to avoid protruding attachment elements on the top side of the screen surface.
Although screen elements or screen grids shown in the prior art are described as being removable and often exchangeable, none of the screen grids or screen elements include means for assisting in the placement and removal of the screen grids or screen elements within the separating apparatus. Accordingly, many of the prior art separating devices must utilize more than one person to position and remove the screen grid or screen element from that area of the separating apparatus where the screen resides, this area typically being the frame of the separating apparatus. Often times, different screen sizes are used to separate and recycle different types of material. Therefore, there is a need for a separating apparatus which enables the easy placement and removal of removable screen grids or screen elements within and out of the separating apparatus. Therefore, there is also a need for a removable screen assembly for utilization within a separating apparatus which includes elements specifically provided to enable the quick and easy placement and removal of the screen assembly or interchangeable screen assemblies which comprises part of the separating apparatus.